How do you address a problem without bringing up the past?

[anjlbeing]

Basically, I have a friend that sometimes makes excuses for breaking plans with me, takes advantage of my unconditional support, and makes time for guys, but cuts things short with me. She tries to make me feel sorry for her sometimes, and puts me on a guilt trip if I try to tell her she has hurt me. If I give her space or she feels that I am upset, she tries to rectify things and becomes very needy. It's like she wants to have her cake and eat it too. I've been trying to talk to her about a recent incident where we had plans, and I didn't hear from her until she wanted to talk about something bad that happened the night before...She craves attention from me, but hurts me in the end. Before this minor situation blows up, I need to tell her how I feel she is taking advantage of me and is only here for me when it's convenient, but it's been in the PAST, and I don't know how to address the past without making her defensive. She's the type that will say things to make me feel sorry for her when I'm trying to tell her I've been hurt. She can't focus on one thought due to her ADHD, and she can't carry on a normal conversation. In a way, I feel that it's not fair to her, but it has never been dealt with, and I feel a little resentment but don't know if I should get it cleared and really know that she's here for me, or just move forward and forgive and forget to save the friendship.